From: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date: Fri, 21 Oct 2022 11:35:33 +0000 (+0100)
Subject: cheri: malloc: Ensure the mappings have RW permission
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=44283b4f2ff4dd8976209b6438e4279a0f3f07d5;p=thirdparty%2Fglibc.git

cheri: malloc: Ensure the mappings have RW permission

The arena allocator incrementally applies RW mprotect to a PROT_NONE
mapping.  Use PROT_MAX to ensure the pointers derived from the original
mapping have RW capability permission.
---

diff --git a/malloc/malloc.c b/malloc/malloc.c
index cc222eaba2f..392116a5ac9 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -1284,8 +1284,16 @@ static mchunkptr mremap_chunk(mchunkptr p, size_t new_size);
 # define MAP_NORESERVE 0
 #endif
 
+/* Allow RW mprotect later, on CHERI this means RW capability permission.  */
+#ifdef PROT_MAX
+# define PROT_MAX_RW PROT_MAX (PROT_READ | PROT_WRITE)
+#else
+# define PROT_MAX_RW 0
+#endif
+
 #define MMAP(addr, size, prot, flags) \
- __mmap((addr), (size), (prot), (flags)|MAP_ANONYMOUS|MAP_PRIVATE, -1, 0)
+ __mmap((addr), (size), (prot)|PROT_MAX_RW, \
+	(flags)|MAP_ANONYMOUS|MAP_PRIVATE, -1, 0)
 
 
 /*